Patent GB-868375-A (GB)
Title: Improvements in or relating to control systems for sewing and the like machines
IPC: G05B19/14
Filed: 1958-02-28
Abstract: 868,375. Sewing &c. machine control apparatus. PFAFF A.G., G. M. Feb. 28, 1958 [Feb. 28, 1957], No. 6483/58. Addition to 844,617. Class 40(3) [Also in Group VII] In a position control apparatus according to the parent Specification for advancing a workpiece of a sewing or like machine from one operating position to another, a card or striplike programme selector serves for the adjustment of the electrical pulse counter and may also effect control over thread cutters, edge trimmers or other additional devices of the sewing &c. machine. In one arrangement a perforated tape 218, Fig. 3a, controls a sewing programme for the sewing of a seam of a predetermined number of stitches and cutting of the thread, the advance of the workpiece by a given distance followed by the sewing of another seam of predetermined number of stitches and the simultaneous edge trimming of the work followed by a return of the work through the given distance, after which the tape 218 returns to its initial position so that the entire programme may be repeated on another workpiece. After closing a power supply switch 269, Fig. 3a, a key 271 is closed to energize a magnet 144 which attracts an armature 145 which is held in the attracted position by a pawl 262. The armature 145 operates a plurality of switches 249, 254, 257. The switch 257 sets the counting tubes 37, 38, 39 to the number "999" for control and monitoring purposes; the switch 254 applies potential to terminal f4 of a step switch 210 to prepare the switch 210 to operate a thread cutter magnet 214 at a later stage; the switch 249 energizes a drive motor 122 of the tape 218, thus driving the take-up drum 160. Closing of the key 271 also sets the selector switches 123, 124, 125 of the electronic counter 3 to zero. During movement of the tape 218, perforations in rows 129, 130, 131, permits contact fingers 132, 133, 134 to make contact with the contact plate 121, producing current pulses by which the selector switches 123, 124, 125 are set to a number determined in accordance with the number of stitches required in the first seam. Also holes in a row 219 of the tape produce current impulses which are applied to a step switch 209, by means of which a photoelectric cell 313, Fig. 3b, is connected to the counter 3. By a hole in a row 138 of the tape 218 a pulse is applied to a magnet 140 which operates the pawl 262, to release the armature 145, whereby, the tape driving motor 122 is disconnected by the switch 249, the counter 3 is set to the number preselected on the switches 123, 124, 125 by the switch 257, and the operating magnet 215 of the motor 205 is energized by the switch 249 to start the sewing machine. A disc chopper 311 and a light source 314 produce a pulse in the photo-cell 313 for each revolution of the sewing machine, these pulses being applied to the counter 3 which after completion of the required number of stitches closes its contact 41. The contact 41 is in parallel with the key 271 so that when it closes the various switches are again set as already described for the operation of the key 271. The tape 218 is once again running and by means of perforations in the row 220, the step switch 210 is operated to energize a magnet 214 of the thread cutter 202. A perforation in the row 221 of the tape 218 then causes the return of the step switch 210 to its rest position. Continued operation of the tape 218 sets the selector switches 123, 124, 125 to a number in accordance with the distance through which the workpiece is to be fed in the next stage of the programme, sets a step switch 209 to a position in which the photo-electric cell 20 is connected to the counter 3, causes operation of a workfeed motor 1 and stops the tape driving motor 122. The workpiece is then fed by a distance determined by the setting of the counter 3, in the manner described in Specification 844,617, the feed being stopped when the contacts 41 close. Closing of the contacts 41 again resets the switches and starts the tape 218 so that the apparatus is set to sew the second seam of a predetermined number of stitches, the step switch 210 being operated by perforations in the row 220 of the tape 218 so that the magnet 213 of the edge trimmer 203 is energized. After sewing the second seam, the tape 218 is again started whereby the counter selector switches are reset and the workpiece feed motor reconnected by a reversing switch 211 to run in a reverse direction so that the workpiece is returned through a predetermined distance. The tape is again automatically started, setting the selector switches 123, 124, 125 to the number 995 and connecting a photo-electric cell 231 to the input of the counter 3. The tape drive motor is then automatically disconnected, its shaft 157 is uncoupled from the drum 160 and coupled to the tape supply drum 161 and the motor 122 then reconnected to rewind the tape on to the drum 161. The tape 218 is provided with five perforations in a row 222 which together with a light source 232 produce impulses in the photoelectric cell 231 which operates the counter 3 so that the contacts 41 are again operated, in response to which the motor 122 is switched off, recoupled to the drum 160 and re-energized to advance the tape into its original position in preparation for a repeat of the entire programme by renewed closing of the key 271. In another arrangement, Fig. 1 (not shown), having a control circuit similar to the circuit described in Specification 844,617 a perforated tape is employed to preset the electronic counter selector switches for each step in a buttonhole sewing programme.